Quando se achava que não se poderia inventar nada mais sobre threads, eis que vem o Ingo (Molnar) e implementa algo fundamentalmente novo e elegante.

Leitura obrigatória: Linux: Syslets & Threadlets | KernelTrap

Um pequeno resumo:

“‘threadlets’ are basically the user-space equivalent of syslets:
small functions of execution that the kernel attempts to execute
without scheduling. If the threadlet blocks, the kernel creates a real
thread from it, and execution continues in that thread. The ‘head’
context (the context that never blocks) returns to the original
function that called the threadlet.“

Enjoy!